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History: the first successful operations on the heart (repair of wounds, mitral commissurotomy) were followed by open-heart surgery after the invention of the heart-lung machine (Gibbon, 1953). Surgical anatomy: the heart lies in the middle mediastinum inside the pericardium, with the right atrium and right ventricle anteriorly. The aorta, pulmonary trunk, superior and inferior vena cavae and coronary arteries are the key structures. Median sternotomy: a midline skin incision and division of the sternum with a saw, opening the pericardium to expose the heart. Minimally invasive approaches (mini-thoracotomy, robotic, transcatheter) are used for selected procedures. Complications of sternotomy: bleeding, infection (mediastinitis), sternal instability.

Cardiopulmonary bypass (CPB): venous blood is drained from the right atrium or venae cavae to a reservoir, oxygenated and cooled or warmed in an oxygenator, and returned by a pump to the ascending aorta (arterial cannula), with systemic heparinisation (activated clotting time above 400 s; reversed at the end with protamine). The aorta is cross-clamped to give a still, bloodless field. Myocardial protection: cardioplegia (a cold, hyperkalaemic solution given into the aortic root or coronary sinus) arrests the heart in diastole, and hypothermia reduces metabolic demand. Effects of CPB: systemic inflammatory response, bleeding from platelet dysfunction, embolic and neurological complications, and renal injury. Off-pump surgery avoids CPB in selected coronary operations.

1. What is median sternotomy? 2. Describe how cardiopulmonary bypass works. 3. What is the purpose of cardioplegia? 4. How is heparin reversed after bypass?

1. A midline division of the sternum giving access to the heart. 2. Blood is drained from the venous system, oxygenated and returned to the aorta by a pump, bypassing heart and lungs. 3. To arrest the heart in diastole and protect the myocardium during cross-clamping. 4. With protamine.

Coronary anatomy: the left main artery divides into the left anterior descending (LAD) and circumflex arteries; the right coronary artery (RCA) supplies the right heart and, in right-dominant hearts (about 85 percent), gives the posterior descending artery. Dominance is defined by the artery that gives the posterior descending branch. Indications for CABG (improves survival): significant left main disease, three-vessel disease especially with reduced left ventricular function or diabetes, proximal LAD disease with multivessel involvement; complexity is scored with the SYNTAX score. PCI is preferred for one- or two-vessel disease without proximal LAD involvement, and in acute STEMI.

Left internal mammary (thoracic) artery to the LAD: patency over 90 percent at 10 years and survival benefit. Other conduits: great saphenous vein (patency about 50-60 percent at 10 years), radial artery and the right internal mammary artery. Multiple arterial grafting improves long-term results in suitable patients. Postoperative therapy: aspirin, statin, beta-blocker, risk factor control.

1. Which grafts have the best long-term patency? 2. State indications for CABG over PCI. 3. How is coronary dominance defined?

1. The left internal mammary artery to the LAD (over 90 percent at 10 years). 2. Left main disease, three-vessel disease (especially with diabetes or reduced ventricular function) and complex proximal LAD disease. 3. By the coronary artery that gives the posterior descending artery (usually the right coronary artery).

Aortic stenosis (calcific degeneration, bicuspid valve, rheumatic disease): symptoms angina, syncope and heart failure; severe when the valve area is below 1 cm squared or mean gradient is at least 40 mmHg. Treatment: valve replacement. Surgical aortic valve replacement (SAVR) with a mechanical prosthesis (durable; lifelong warfarin) or a biological prosthesis (bioprosthesis; limited durability, less anticoagulation) or transcatheter aortic valve implantation (TAVI), preferred in older or high-risk patients and increasingly in intermediate-risk ones. Choice depends on age, risk, anatomy and patient preference.

Mitral regurgitation (degenerative from prolapse, functional from ventricular dilation, rheumatic, endocarditis) and stenosis (mainly rheumatic). Repair (annuloplasty ring, leaflet resection, neochordae) preserves the native valve and left ventricular function, avoids long-term anticoagulation and has lower operative mortality than replacement. Replacement with a mechanical (young patients; warfarin) or biological prosthesis when repair is impossible. Transcatheter edge-to-edge repair is an option for high-risk patients.

Indications: valvular dysfunction causing heart failure, uncontrolled infection (abscess, persistent bacteraemia, resistant organisms, fungi) and large vegetations with embolic events. Surgery removes infected tissue and repairs or replaces the valve. Timing after a stroke: haemorrhagic stroke or large infarcts require delay, whereas after a small embolic infarct early surgery is usually feasible; the risk of further embolism must be weighed against neurological worsening.

Risk factors: hypertension, connective tissue disease (Marfan syndrome), bicuspid aortic valve, aortic aneurysm, trauma. Presentation: sudden severe tearing chest or back pain, pulse or blood pressure differences between arms, aortic regurgitation, tamponade or malperfusion. Diagnosis: CT angiography. Stanford classification: type A (involves the ascending aorta): emergency surgery (replacement of the ascending aorta, with arch procedures if needed), because of the risk of rupture, tamponade and coronary or aortic valve involvement. Type B (descending aorta only): medical therapy (impulse control with intravenous beta-blockers, pain relief and blood pressure control) with endovascular repair (TEVAR) for complications. DeBakey classification is an alternative.

1. Compare mechanical and biological valve prostheses. 2. Why is mitral valve repair preferred to replacement? 3. List indications for surgery in endocarditis. 4. How are Stanford type A and type B dissections treated?

1. Mechanical: durable but needs lifelong warfarin. Biological: shorter durability but little or no anticoagulation. 2. It preserves the native valve and ventricular function, avoids anticoagulation and has lower operative mortality. 3. Heart failure from valve dysfunction, uncontrolled infection and embolic risk from large vegetations. 4. Type A: emergency surgery. Type B: medical therapy, with endovascular repair for complications.